The detection of the concentration level of glucose or other analytes in certain individuals may be vitally important to their health. For example, the monitoring of glucose levels is particularly important to individuals with diabetes or pre-diabetes. People with diabetes may need to monitor their glucose levels to determine when medication (e.g., insulin) is needed to reduce their glucose levels or when additional glucose is needed.
Devices have been developed for automated in vivo monitoring of analyte concentrations, such as glucose levels, in bodily fluids such as in the blood stream or in interstitial fluid. Some of these analyte level measuring devices are configured so that at least a portion of the devices are positioned below a skin surface of a user, e.g., in a blood vessel or in the subcutaneous tissue of a user. As used herein, the term analyte monitoring system is used to refer to any type of in vivo monitoring system that uses a sensor disposed with at least a portion subcutaneously to measure and store sensor data representative of analyte concentration levels automatically over time. Analyte monitoring systems include both (1) systems such as continuous glucose monitors (CGMs) which transmit sensor data continuously or at regular time intervals (e.g., once per minute) to a processor/display unit and (2) systems that transfer stored sensor data in one or more batches in response to a request from a processor/display unit (e.g., based on an activation action and/or proximity, for example, using a near field communications protocol) or at a predetermined but irregular time interval.
Determining an analyte concentration level in blood based on the analyte concentration measured using an analyte monitoring system typically involves calibrating the in vivo sensor of the analyte monitoring system using a reference measurement. For example, a finger stick blood sample may be used as a reference to determine the blood analyte concentration at a particular time and the result is paired with a corresponding measurement from the analyte monitoring system. The sensitivity of the analyte monitoring system's sensor is adjusted based on the difference and other factors. However, several factors related to the measurement from the analyte monitoring system can affect the accuracy of the calibration. Thus, what is needed are systems, methods and apparatus to improve sensitivity calibration of the in vivo sensors used to measure analyte concentration.